Whenever a serious incident takes place in a school chemistry laboratory or classroom, fire and safety officers often pontificate on the incident by quoting the Materials Safety Data Sheet (MSDS). However, how many of you have read such documents in full? In UK schools we have perhaps 200 to 400 chemicals on the shelves. Have you read the MSDSs for each chemical? Did you even know there was such a thing as a MSDS or do you just “always read the label”. In the UK, we have many very experienced school laboratory technicians who do have access to the MSDSs and to a large extent, protect the teacher and so I suspect there are many teachers who do not know that they exist. If they had been told about them, it was years ago in University perhaps. In the UK and the USA, we have to store the MSDS sheets electronically or in a filing cabinet. I suspect once in the storage area they are never read.
They are silly
This statement may seem impudent in the extreme. After all, many really well-qualified chemists and toxicologists in the United Nations, Occupational Safety & Health Administration (OSHA), European Chemical Agency (EChA), Health and Safety Executive(HSE) and countless other organisations in all the developed countries in the world have spent many hours of serious debate and research on implementing GHS. The aim is to ensure that the same information is available on chemicals no matter which continent you are in.
Yet I can show the section on sodium chloride and sterile water in Figs 1a and 1b to any experienced chemistry teacher and the response will be “This is silly”.
Figure 1a from a MSDS for sodium chloride
Figure 1b from a MSDS for First Aid measures for exposure to sterile water
You can imagine the coffee-time discussion amongst teachers and lecturers of chemistry discussing and ultimately dismissing these documents in no uncertain terms as “unbelievable”. The issue now is that the MSDS loses its credibility amongst the experienced chemists; that can be dangerous and a complete disregard of the use of MSDS may be illegal.
It is obvious that a computer is at work but with companies supplying thousands of chemicals mostly to Industry, Hospitals and Universities and only a small percentage to Schools and Colleges I hope you can see the suppliers’ problem. The format of these MSDS documents are enshrined in the advice from the United Nations.
They are simply wrong
UK schools have informed CLEAPSS of any hazards which seemed to be different from those they had previously received. I remember the first one. Vaseline (usually no hazard classification) was ordered by a school from a supplier but it came with a carcinogen warning. The school contacted the educational supplier but the reply was “It is the new laws”. It was only when the school contacted our organization, worried that they had been using a substance which was carcinogenic, for tens of years with students that we managed to get the supplier to go to their supplier to confirm that the wax should not be classified as carcinogenic. Now, there was a reason for the hazard warning because if any supplier was taking the information from the ECHA website, Petrolactum or Vaseline did carry a carcinogen warning but with this comment: “The classification as a carcinogen need not apply if the full refining history is known and it can be shown that the substance from which it is produced is not a carcinogen”. This comment is easily missed. The suppliers have made other mistakes and poor interpretations of the law. They are learning to cope with the new legislation as it is acknowledged to be very complicated. What teachers might not realise is that a MSDS is generated when the chemical enters or is manufactured in the country. The information has to be passed down to the next outfit in the supply chain and so on until your school buys the chemical. In this game of “whispers” mistakes are bound to happen.
A sole teacher in a small school was frightened to open a bottle of magnesium powder (required by an exam board for an assessed practical exam) because on the label it said H250: Catches fire spontaneously if exposed to air. Again, there had to be careful reading of the documentation because a Note said that “This substance may be marketed in a form which does not have the physical hazards as indicated by the classification”.
The UK is fortunate to have a HSE Helpline, The Environment Health & Safety Committee at the Royal Society of Chemistry and the Chemical Hazards Communication Group (industrial) for advice and help. The HSE and the RSC are vociferous in their support of chemistry practical work in schools. It is necessary to work with the system and not against it.
They are emotive
What does the word “fatal” conjure up in your mind? “There has been a fatal accident” on the news suggests a person has immediately died but in GHS speak it means very toxic. Figure 2 is taken from a supplier’s MSDS sheet on sebacoyl chloride, a chemical we use in the UK in schools to do the “nylon rope experiment” and CLEAPSS received a number of calls on the word “fatal” and the question “is it banned?” In fact, the degree of hazard had not changed from before GHS, but then it was written as “very toxic in contact with the skin” and nobody made a comment about that. In fact I actually poured 2 to 3 ml of this solution on my hand, washed it off and I am still here.
The hazard ratings for chemicals are not given “on the nod” but need criteria as provided in guidance in a document called the Purple Book. The testing criteria can be found in the Organisation for Economic Cooperation and Development Library. It does involve animal testing but one is assured this is kept to a minimum. Because of the complexity of the area, suppliers do get it wrong, especially as countries adopt the new GHS system, and if it seems wrong to you, your professional body may be the first point of call as they do have a safety section. Communicating this information to non-scientists or even scientists of a different persuasion can be difficult.
They do not take into account dilution (“The dose makes the poison” – Paracelsus)
The school buys sodium hydroxide pellets. The teacher/technician makes a solution and dilutes the solution to 0.1M. The MSDS sheet is only relevant to the person making the solution as it makes no comment about dilution. Even if you buy a dilute solution, the true hazard classification of the product can be hidden in the wording of the MSDS sheet. I have seen MSDS sheets for 0.2M sodium hydroxide which quote the hazards of solid sodium hydroxide with no mention of the reduction of hazard caused by dilution.
These cut off concentrations differ for every substance because it is calculated by percentage by mass of substance or element present. So the dividing lines for dilution effects are different for potassium and sodium hydroxide solutions. I once questioned this and was told the mole concept is not well understood. Having taught it and knowing the difficulties, I agreed but also wondered why we teach it if industry does not use it!
CLEAPSS does have direct evidence for the severity of the hazard when a 2M solution was poured over a student’s eye in a fight (not a Health & Safety issue, this is assault) and caused blindness but when solutions below 0.5M have ever entered the eye and eye irrigation has been applied, there has been no permanent damage.
Naturally, the same applies to toxic chemicals. Copper(II) sulfate(VI) solutions lose the Harmful if swallowed warning at concentrations less than 1M and solutions at concentrations less than 0.6M have no hazard warning. This does not mean that teachers have a free hand to do what they like with 0.5M copper(II) sulfate(VI) solution; good laboratory etiquette is important at all times.
The changes to hazard classification with dilution are very important when it comes to carrying out risk assessments.
They do not take into account exposure time
I hope you now realise that the MSDS, although useful, is more relevant to those in industry who are working with a chemical 8 hours a day for a year. Obviously, in those conditions the degree of exposure is considerably higher. The word “exposure” is unfortunate because in law and the tabloid press, it can mean all sorts of unsavory habits of certain individuals with weird minds. In the world of toxicology, looking at a chemical such as lead nitrate is not going to cause you a problem. Exposure means intake into the body by 3 possible routes, ie, inhalation, ingestion and through the skin (the dermal and ocular route). Some chemicals do have an immediate effect (acute); sulfur dioxide and chlorine can cause breathing difficulties but we, as teachers, should know this and use appropriate control measures to minimise exposure. I use a microscale method of electrolyzing copper chloride solution which produces only about 6 cm3 of gas in a Petri dish. If I am reacting chlorine in a gas jar with sodium or iron, I would use a fume hood (cupboard), which vents the gas to the atmosphere or absorbs it into a filter.
There are now hazard warnings about borax causing harm to the unborn child but the evidence is from mining the solid with poor safety instructions. Nickel solutions cause nasal cancers but the evidence comes from badly controlled electroplating works. The route is via inhalation of nickel so how is that going to happen in a school laboratory? Reacting nickel carbonate with acid and electroplating nickel can cause an aerosol. In the UK, despite the degree of exposure being very tiny, we still warn and will take effective methods. Zinc electroplating illustrates the procedure just as well as nickel electroplating and can be used as a substitute.
They do not take into account volume and amount
Teachers may now regard with some justification that the information in relation to toxicity, both chronic and acute MSDS is more relevant to industry where employees may be in contact with large amounts of material possibly as a dust or aerosol for the working day and throughout the year. This regular contact can seriously affect health.
The MSDS sheet does not take into account the tiny amounts of material used by teachers and students. However, we have already seen that the information on flammability, acute toxicity, corrosion and irritation to the eyes and skin is important. Please remember that corrosion is not about rusting but the destruction of body cells.
Using smaller amounts is even more important with flammable materials. Both in the USA and UK, people have been badly burned with liquids such as alcohols catching fire and there are large outcries to ban the chemicals used. In the UK a boy was badly burned on the chest (made worse with a rubber lined T-shirt underneath), leaning over a tea-light. Should we ban tea-lights, candles in restaurants, etc? It is constant vigilance and training on the part of the teacher and technician which matter and, more importantly, a realisation that the school-science staff need continual professional development, training etc. In the UK, senior management have a duty of care to monitor that science teachers are adhering to the rules (I don’t think they or anyone in Industry likes this, it but it is enshrined in our Health and Safety Law; it would be easier to simply blame and sack the teacher for an incident. ).
Teachers love teaching and they love to enthuse the students in a wonderful subject and they can easily push the boundaries too far by making a demonstration bigger. They see lecturers in lecture halls burst large balloons of hydrogen and oxygen, do “Liebig’s barking dog”, light large soap bubbles of methane or hydrogen (NOT LPG), in the air or their hands, breathe in helium and sulfur hexafluoride to affect the pitch of their voices. It all looks very easy but these lecturers rehearse and rehearse these demonstrations. (I call them edutainers!)The teacher cannot simply take these demonstrations into the classroom without a lot of research, training and practice. Balloons of hydrogen and oxygen are too loud for a small room and can cause deafness, Liebig’s barking dog can explode (as it did when he did it), burning gases on the hands can cause serious burns especially if LPG is used and inhaling gases is just bad practice in a school context as it can lead to bad habits by students.
They do not take into account the products of a chemical reaction
Seawater is about a 0.05M solution of sodium chloride. It is not classified as hazardous although with large exposure it can kill by ingestion of large volumes, it can be absorbed through the skin (ocean swimmers grease themselves) and breathing it in is pretty dangerous too! In the laboratory, I can put 2 carbon electrodes in sea water, connected to a low voltage supply, and generate chlorine, a highly toxic gas which can upset students with asthma. But there is no MSDS for chlorine as I do not buy the gas.
0.05 M sodium thiosulfate and 1M hydrochloric acid are not classified as hazardous but mix them together and sulfur dioxide is formed, a toxic gas. You do not have a MSDS for sulfur dioxide because you do not buy it. I cite both of these experiments because they have both caused students to be taken to hospital for checks on breathing and the inevitable call from safety officers and school managers as to why we are subjecting students to distress. These were activities set by examination boards for assessment. In both cases the teachers involved were not chemists by training and the lessons got out of hand. The exam had been set by experienced chemistry specialists who knew (and probably thought all teachers knew) about the hazards of the products.
It has taken 20 years for a reduced scale method developed by CLEAPSS to be finally accepted by one of our exam boards to be an accepted method of carrying out the reaction. The other essential part of this method is to pour the products of the reaction into a stop-bath of sodium carbonate solution which stops the reaction and neutralises the sulfur dioxide.
They are not risk assessments
Many articles on chemistry experiments cite hazards. The teacher should be more concerned about risk, the chances of an incident taking place and the potential severity/extent of harm that may be caused. Teachers of science need to demonstrate to senior management that they have reduced the possibility of an incident taking place and to ensure the use of the most comfortable personal protective equipment as the last resort. They can show this by including the method and relevant control measures in their schemes of work (SOW). As well as columns in SOW to please educational inspectors (e.g., learning objectives), there needs to be a column which shows that the teacher understands the possible risks from an activity and has taken steps (control measures) to reduce them. Both teachers and senior management should be aware that risk cannot be totally eliminated. The important factor is not to make a recorded risk assessment a huge multi-page document which will end up stored in a filing cabinet and never read (teachers do not have the time), but a few simple sentences to remind yourself (you might only do this activity once a year) and to remind your other colleagues who may take a lessons in chemistry. Lowering the concentration of a solution to a level which still illustrates what you are trying to show and has the smaller number of hazard statements is one way of showing that you applying risk assessments (hazard analysis). Teachers can add 0.4M sodium hydroxide solution to 0.1M copper(II) sulfate(VI) solution and still obtain a beautiful precipitate, instead of using 1M solutions which are far more hazardous for students to use. I can reduce the risks further by placing drops of these reagents on a plastic sheet.
If a teacher makes an improvement in safety, the SOW can be easily altered. The teachers’ risk assessment needs to look at how the chemicals are presented to students so this improvement on classroom management, is a part of the risk assessment.
It is important to focus on the relevant risks. In the last few years, boron compounds, used in producing green flames with methanol, have been given a hazard waning that they can cause harm to the unborn child. I have had teachers on the phone worried sick that they have used boric acid when they themselves or the students are of child bearing age. The fact that methanol is very flammable, as highlighted in a recent report by the Chemical Safety Bureau of serious fires in schools, and acutely toxic is never considered as the main risk. After all, it can be bought in Car shops in the USA so it must be safe. No!
You need training in how to use them
The teacher may be involved with over 400 chemicals in the year used in small amounts, for a few minutes and perhaps once a year. The industrial worker may be involved with 2 chemicals used in tonnes and litres (gallons) for the whole working year. The chemistry teacher might carry out 400 single operations with hazards in the year. The industrial worker might carry out only 2 hazardous operations but they are repeated daily and all through the year. Both situations have their dangers in complacency.
It often comes as a surprise to both teachers and educational managers that hazard analysis (https://www.osha.gov/Publications/osha3071.html) or Risk Assessment is important for any work with hazardous chemicals with the MAIN findings recorded. Fig 4 is taken from the UK HSE website.
Figure 4: From the UK HSE Website
Very little quality training in safety is really offered in teacher training. The problem with safety training is that it can, in the hands of some, be a frightening list of ‘don’t do this’ and ‘don’t do that’. It can sometimes be over-emotive and worst of all, patronising. Safety training works best when it shows how procedures should be carried out and then by monitoring in a sensitive manner. This is best done by experienced practitioners (often retired), ideally with the blessing of relevant advisory bodies and subject institutions. A local Health and Safety Officer from the Armed Forces, an expert in Heavy Lifting and grave digging and, dare I say it, large-scale chemistry engineering or a recent graduate in science is not always the right person to deliver this training to teachers of chemistry.
Bob Worley FRCS, MSc, BSc (semi-retired advisor for Chemistry at CLEAPSS, UK)